Nitrogen-fixing Microorganisms Research Articles

The Spatial Dynamics of Diazotrophs in the Forefield of Three Tibetan Glaciers.

Nitrogen is often a limiting nutrient for microbial communities and plants in glacier forefields. Nitrogen-fixing microorganisms (diazotrophs) play an important role in providing bioavailable nitrogen, with their composition determining the nitrogen-fixating capacities. This study investigates the spatial and temporal dynamics of diazotrophs in the forefields of three Tibetan glaciers: Qiangyong, Kuoqionggangri, and Longxiazailongba. We collected soil samples from recently deglaciated barren grounds, and also along an ecosystem succession transect at Kuoqionggangri glacier, encompassing barren ground, herb steppe, legume steppe, and alpine meadow ecosystems. Our finding revealed abundant and diverse diazotrophs in the recently deglaciated barren ground. They are taxonomically affiliated with anaerobic Bradyrhizobium, Desulfobulbus, and Pelobacter, which may be relics from subglacial sediments. The vegetated soils (herb steppe, legume steppe, and alpine meadow) were dominated by phototrophic Nostoc and Anabaena, as well as symbiotic Sinorhizobium. Soil physicochemical parameters, such as soil organic carbon, pH, and nitrate ion, significantly influenced diazotroph community structure. This study highlights the critical role of diazotrophs in mitigating nitrogen limitation during early ecosystem development in glacier forefields. Understanding the distribution and ecological drivers of diazotrophs in these rapidly changing environments provides insights into biogeochemical cycling and ecosystem resilience under climate change.

Temporal dynamics of the diazotrophic community during corpse decomposition

Corpse decomposition affects soil organisms through the formation of “cadaver decomposition islands.” Soil diazotrophic microbes possess essential ecological functions on nitrogen input and nutrient cycling in the terrestrial ecosystem. However, our knowledge about how soil diazotrophic communities respond to corpse decomposition is lacking. In this study, we focused on the succession patterns and biological interaction of nitrogen-fixing microorganisms during animal (Ochotona curzoniae) corpse decomposition in terrestrial ecosystems by targeting nifH gene with high-throughput sequencing. Our results revealed that corpse decomposition of pikas reduced the α diversity and significantly impacted the β diversity of diazotrophic community across different decomposition stages. The divergent succession of diazotrophic community occurred under corpse pressure. Furthermore, the relative importance of stochasticity to the community assembly was improved by corpse decomposition, while the importance decreased over decomposition time. Cadaver decay also simplified the diazotrophic networks and weakened the biological interactions among diazotrophic populations. Notably, NH4-N was the most important factor affecting diazotrophic community, followed by time and total carbon. This work emphasized that corpse decomposition perhaps influences the process of biological nitrogen fixation by altering soil diazotrophic communities, which is of great significance for understanding the terrestrial ecosystems’ nitrogen cycle functions.Key points• Corpse decomposition reduced the α diversity of diazotrophic community.• Corpse decomposition improved the stochasticity of diazotrophic community assembly.• Corpse decomposition weakened the interactions among diazotrophic populations.

Inoculation with Azospirillum brasilense as a Strategy to Reduce Nitrogen Fertilization in Cultivating Purple Maize (Zea mays L.) in the Inter-Andean Valleys of Peru.

Purple maize has gained global significance due to its numerous nutraceutical benefits. However, sustaining its production typically requires high doses of nitrogen fertilizers, which, when applied in excess, can contaminate vital resources such as soil and water. Inoculation with nitrogen-fixing microorganisms, such as those from the Azospirillum genus, has emerged as an alternative to partially or fully replace nitrogen fertilizers. This study aimed to evaluate the inoculation effect with A. brasilense and varying nitrogen fertilization levels on the yield and quality of purple maize. The experiment was carried out using a randomized complete block design (RCBD) with a 2 × 5 factorial arrangement and five replications. Treatments comprised two inoculation levels (control without inoculation and inoculation with A. brasilense) under five nitrogen doses (0, 30, 60, 90, and 120 kg∙ha-1, applied as urea). Inoculation with A. brasilense resulted in a 10.5% increase in plant height, a 16.7% increase in root length, a 21.3% increase in aboveground fresh biomass, a 30.1% increase in root fresh biomass, and a 27.7% increase in leaf nitrogen concentration compared to the non-inoculated control. Regarding yield, the inoculated plants surpassed the control in both purple maize yield (kg∙ha-1) and cob weight by 21.8% and 11.6%, respectively. Across all fertilization levels and parameters assessed, the inoculated treatments outperformed the control. Furthermore, for parameters, namely plant height, leaf nitrogen content, and cob dimensions (length, diameter, and weight), the A. brasilense inoculation treatment with 90 kg N∙ha-1 was statistically equivalent or superior to the non-inoculated control with 120 kg N∙ha-1. These results indicate that inoculation with A. brasilense positively impacted purple maize at all nitrogen levels tested and improved nitrogen use efficiency, enabling a reduction of 30 kg N∙ha-1 without compromising performance in key parameters.

Nitrogen-Fixing Gamma Proteobacteria Azotobacter vinelandii—A Blueprint for Nitrogen-Fixing Plants?

The availability of fixed nitrogen limits overall agricultural crop production worldwide. The so-called modern “green revolution” catalyzed by the widespread application of nitrogenous fertilizer has propelled global population growth. It has led to imbalances in global biogeochemical nitrogen cycling, resulting in a “nitrogen problem” that is growing at a similar trajectory to the “carbon problem”. As a result of the increasing imbalances in nitrogen cycling and additional environmental problems such as soil acidification, there is renewed and increasing interest in increasing the contributions of biological nitrogen fixation to reduce the inputs of nitrogenous fertilizers in agriculture. Interestingly, biological nitrogen fixation, or life’s ability to convert atmospheric dinitrogen to ammonia, is restricted to microbial life and not associated with any known eukaryotes. It is not clear why plants never evolved the ability to fix nitrogen and rather form associations with nitrogen-fixing microorganisms. Perhaps it is because of the large energy demand of the process, the oxygen sensitivity of the enzymatic apparatus, or simply failure to encounter the appropriate selective pressure. Whatever the reason, it is clear that this ability of crop plants, especially cereals, would transform modern agriculture once again. Successfully engineering plants will require creating an oxygen-free niche that can supply ample energy in a tightly regulated manner to minimize energy waste and ensure the ammonia produced is assimilated. Nitrogen-fixing aerobic bacteria can perhaps provide a blueprint for engineering nitrogen-fixing plants. This short review discusses the key features of robust nitrogen fixation in the model nitrogen-fixing aerobe, gamma proteobacteria Azotobacter vinelandii, in the context of the basic requirements for engineering nitrogen-fixing plants.

Depth-dependent Effects of Leguminous Crops on Soil Nitrogen-Fixing Microbial Communities Correlated with Carbon Degradation

Abstract Legumes play critical roles in agroecosystems by modulating nitrogen-fixing microorganisms to enhance soil fertility and promote crop productivity. Current research on the effects of legumes predominantly focuses on surface soil, lacking a comprehensive analysis of their overall impact across multiple soil layers and an in-depth understanding of associated microbial mechanisms. Here, the community structure of soil nitrogen-fixing microorganisms in three soil layers (0-20, 20-50, and 50-100 cm) under legume and non-legume cultivation was investigated through metagenomic sequencing. We found that only in topsoil (0-20 cm) legume treatment exhibited a significantly higher relative abundance of nitrogen-fixing genes than non-legume treatment. Under legume cultivation, the relative abundance of nitrogen-fixing genes was significantly higher in the topsoil layer than in deeper layers, whereas non-legume treatment displayed an inverse depth-dependent pattern. Combining soil physicochemical properties, the relative abundance of nitrogen-fixing genes correlated significantly with soil moisture, total carbon (TC), and dissolved organic carbon (DOC) content. Both TC and DOC were identified as key drivers of these genes. Subsequently, a similar depth-dependent pattern within the relative abundance of soil carbon degradation genes was found in response to the cultivation of both crops. The relative abundances of soil carbon degradation genes were negatively correlated with nitrogen-fixing genes under legume treatment individually, distinct from non-legume treatment. Our findings highlight the depth-dependent impact of legumes on nitrogen fixation and the critical interaction between soil carbon degradation and nitrogen fixation, providing insights into carbon management in legume cultivation practices to enhance nitrogen fixation in future agriculture.

Root Endophytic Microorganisms Contribute to the Attribute of Full-Year Shooting in Woody Bamboo Cephalostachyum pingbianense.

Cephalostachyum pingbianense (Hsueh & Y.M. Yang ex Yi et al.) D.Z. Li & H.Q. Yang is unique among bamboo species for its ability to produce bamboo shoots in all seasons under natural conditions. Apart from the physiological mechanism, information regarding the effects of endophytic microorganisms on this full-year shooting characteristic is limited. We hypothesize that root endophytic microorganisms will have a positive impact on the full-year bamboo shooting characteristic of C. pingbianense by increasing the availability or supply of nutrients. To identify the seasonal variations in the root endophytic bacterial and fungal communities of C. pingbianense, and to assess their correlation with bamboo shoot productivity, the roots of C. pingbianense were selected as research materials, and the 16S rRNA and ITS rDNA genes of root endophytic microorganisms were sequenced using the Illumina platform. Following this sequencing, raw sequencing reads were processed, and OTUs were annotated. Alpha and beta diversity, microbial composition, and functional predictions were analyzed, with correlations to bamboo shoot numbers assessed. The results showed that seasonal changes significantly affected the community diversity and structure of root endophytic microbes of C. pingbianense. Bacterial communities in root samples from all seasons contained more nitrogen-fixing microorganisms, with members of the Burkholderiales and Rhizobiales predominating. The relative abundances of ectomycorrhizal and arbuscular mycorrhizal fungi in the autumn sample were significantly higher than in other seasons. Correlation analysis revealed that the bamboo shoot productivity was significantly and positively correlated with bacterial functions of nitrogen fixation, arsenate detoxification, and ureolysis, as well as with symbiotrophic fungi, ectomycorrhizal fungi, and arbuscular mycorrhizal fungi. At the genus level, the bacterial genus Herbaspirillum and the fungal genera Russula, unclassified_f_Acaulosporaceae, and unclassified_f_Glomeraceae were found to have a significant positive correlation with bamboo shoot number. Our study provides an ecological perspective for understanding the highly productive attribute of C. pingbianense and offers new insights into the forest management of woody bamboos.

Soil Giant Phage: Genome and Biological Characteristics of Sinorhizobium Jumbo Phage.

This paper presents the first in-depth research on the biological and genomic properties of lytic rhizobiophage AP-J-162 isolated from the soils of the mountainous region of Dagestan (North Caucasus), which belongs to the centers of origin of cultivated plants, according to Vavilov N.I. The rhizobiophage host strains are nitrogen-fixing bacteria of the genus Sinorhizobium spp., symbionts of leguminous forage grasses. The phage particles have a myovirus virion structure. The genome of rhizobiophage AP-J-162 is double-stranded DNA of 471.5 kb in length; 711 ORFs are annotated and 41 types of tRNAs are detected. The closest phylogenetic relative of phage AP-J-162 is Agrobacterium phage Atu-ph07, but no rhizobiophages are known. The replicative machinery, capsid, and baseplate proteins of phage AP-J-162 are structurally similar to those of Escherichia phage T4, but there is no similarity between their tail protein subunits. Amino acid sequence analysis shows that 339 of the ORFs encode hypothetical or functionally relevant products, while the remaining 304 ORFs are unique. Additionally, 153 ORFs are similar to those of Atu_ph07, with one-third of the ORFs encoding different enzymes. The biological properties and genomic characteristics of phage AP-J-162 distinguish it as a unique model for exploring phage-microbe interactions with nitrogen-fixing symbiotic microorganisms.

Nitrogen Fixation and Growth of Potted Olive Plants through Foliar Application of a Nitrogen-Fixing Microorganism

Given the importance of biological nitrogen (N) fixation in agroecosystems, using inoculants with phyllosphere N fixers effective across various crops would revolutionize agriculture. In this study, the application of an inoculant prepared from Methylobacterium symbioticum was tested on young olive trees. The pot experiment was arranged in a factorial design, with inoculant (Yes and No) and mineral N applied to the soil [0 (N0), 25 (N25), 50 (N50), and 100 (N100) kg ha−1], and four replicates. The inoculant application did not increase plant dry matter yield (DMY), whereas the application of mineral N had a significant and pronounced effect. The inoculant also did not significantly increase N concentration in tissues, unlike the strong increase observed with N applied to the soil. The inoculant significantly increased plant N recovery, a cumulative effect resulting from small increases in DMY and N concentration in tissues. This increase represented 5.2% more N in plants receiving the inoculant compared to untreated ones. However, only treatments receiving mineral N recorded positive values of fixed N, with the highest value observed in the N50 treatment (12.4%), whereas a negative value (−7.7%) was observed in the N0 treatment. Overall, these low values of fixed N question the economic rationale of using this inoculant by farmers and especially render it unsuitable for organic farming systems, where plants tend to have lower N levels in tissues.

Deciphering the Nitrogen Fixation Gene Cluster in Vibrio natriegens: A Study on Optimized Expression and Application of Nitrogenase.

Microbial nitrogen fixation presents a viable alternative to chemical fertilizers, yet the limited colonization and specificity of naturally occurring nitrogen-fixing microorganisms present significant challenges to their widespread application. In this study, we identified a nitrogen fixation gene cluster (VNnif) in Vibrio natriegens (VN) and tested its nitrogenase activity through the acetylene reduction assay. We investigated the potential utilization of nitrogenase by incorporating the nitrogenase gene cluster from VN into plant growth-promoting rhizosphere bacteria Pseudomonas protegens CHA0 and enhancing its activity to 48.16 nmol C2H2/mg/h through promoter replacement and cluster rearrangement. The engineered strain CHA0-PVNnif was found to positively impact the growth of Arabidopsis thaliana col-0 and Triticum aestivum L. (wheat). This study expanded the role of plant growth-promoting rhizobacteria (PGPR) and provided a research foundation for enhancing nitrogenase activity.

Nano molybdenum trioxide-mediated enhancement of soybean yield through improvement of rhizosphere soil molybdenum bioavailability for nitrogen-fixing microbial recruitment

Molybdenum (Mo) plays a pivotal role in the growth and nitrogen-fixing process of plants mediated by rhizobia. However, the influence of nano‑molybdenum trioxide (MoO3NPs) on soybean growth, rhizosphere bioavailable Mo, and nitrogen-fixing microorganisms remains underexplored. Here, we report that compared with that of ionic Mo and bulk MoO3, the utilization of MoO3NPs (specifically NPs0.05 and NPs0.15) significantly boosted the available Mo content in the rhizosphere soil throughout the seedling (by 21.64 %–101.38 %), podding (by 54.44 %–68.89 %), and mature stage (by 34.41 %–to 45.71 %) of soybean growth. Furthermore, both NPs0.05 and NPs0.15 treatments maintained consistently higher levels of acid-extractable Mo, reducible Mo, and oxidizable Mo across these stages, which facilitated stable conversion and supply of bioavailable Mo. Within the rhizosphere soil, NPs0.05 and NPs0.15 treatments resulted in the highest relative abundance of Rhizobiales and Bradyrhizobium genera, and significantly promoted the colonization of nitrogen-fixing microorganisms, thereby increasing the content of nitrate nitrogen (NO3−-N) by 8.69 % and 7.72 % and ammonium nitrogen (NH4+-N) by 44.75 % and 17.55 %, respectively. Ultimately, these effects together contributed to 107.17 % and 84.00 % increment in soybean yield by NPs0.05 and NPs0.15 treatments, respectively. In summary, our findings underscore the potential of employing MoO3NPs to promote plant growth and maintain soil nitrogen cycling, indicating distinct advantages of MoO3NPs over ionic Mo and bulk MoO3.

Agronomic advantage of bacterial biological nitrogen fixation on wheat plant growth under contrasting nitrogen and phosphorus regimes.

Given their remarkable capacity to convert atmospheric nitrogen into plant-accessible ammonia, nitrogen-fixing microbial species hold promise as a sustainable alternative to chemical nitrogen fertilizers, particularly in economically significant crops like wheat. This study aimed to identify strains with optimal attributes for promoting wheat growth sustainably, with a primary emphasis on reducing reliance on chemical nitrogen fertilizers. We isolated free nitrogen-fixing strains from diverse rhizospheric soils across Morocco. Subsequently, we conducted a rigorous screening process to evaluate their plant growth-promoting traits, including nitrogen fixation, phosphate solubilization, phytohormone production and their ability to enhance wheat plant growth under controlled conditions. Two specific strains, Rhodotorula mucilaginosa NF 516 and Arthrobacter sp. NF 528, were selected for in-depth evaluation, with the focus on their ability to reduce the need for chemical nitrogen supply, particularly when used in conjunction with TSP fertilizer and natural rock phosphate. These two sources of phosphate were chosen to assess their agricultural effectiveness on wheat plants. Twenty-two nitrogen-fixing strains (nif-H+) were isolated from various Moroccan rhizospheric soils, representing Bacillus sp., Pseudomonas sp., Arthrobacter sp., Burkholderia sp. and a yeast-like microorganism. These strains were carefully selected based on their potential to promote plant growth. The findings revealed that the application of Rhodotorula mucilaginosa NF 516 and Arthrobacter sp. NF 528 individually or in combination, significantly improved wheat plant growth and enhanced nutrients (N and P) uptake under reduced nitrogen regimes. Notably, their effectiveness was evident in response to both natural rock phosphate and TSP, demonstrating their important role in wheat production under conditions of low nitrogen and complex phosphorus inputs. This research underscores the significant role of nitrogen-fixing microorganisms, particularly Rhodotorula mucilaginosa NF 516 and Arthrobacter sp. NF 528, in wheat production under conditions of low nitrogen and complex phosphorus inputs. It showcases their potential to reduce chemical nitrogen fertilization requirements by up to 50% without compromising wheat plant yields. Our study emphasizes the importance of bacterial biological nitrogen fixation in meeting the remaining nitrogen requirements beyond this reduction. This underscores the vital role of microbial contributions in providing essential nitrogen for optimal plant growth and highlights the significance of biological nitrogen fixation in sustainable agriculture practices.

Effectiveness of sod and humus soil maintenance and biologized protection in intensive apple orchards (Malus domestica Borkh.) in the south of Russia

Application of intensive technologies in horticulture with a high mechanical and chemical load on soils and fruit plants leads to deterioration of soil properties, environmental pollution, and development of resistance among pathogens and phytophages. In this study, we aim to developing a biologized technology for apple tree cultivation using a sod and humus system of inter-row maintenance and biopreparations based on active strains of microorganisms, entomoacariphages, and pheromones. The research was conducted in 2019-2023 in intensive apple orchards of the central plain-steppe region of Crimea by the methods conventionally used in soil science, agrochemistry, horticulture, and plant protection. The use of a mixture of cereal-legume grasses in combination with microbiological fertilizers based on nitrogen-fixing microorganisms was found to increase apple yields by 11–12 t/ha, or 64 % compared to the control, by increasing the number of fruits and the average weight of one fruit. A positive balance of nutrition elements in soil with an intensity of 135-270 % was established. The efficiency of controlling the number of phytophages and pathogen harmfulness through the integrated use of biological and biotechnical methods was shown. Thus, the “attract-and-kill” method for Cydia pomonella L. pheromones demonstrated a 98 % efficiency along with a reduction in pesticide load to 7.7 kg/ha season by the preparation. Release of phitoseiid mites for control of tetranychus mites by the method of seasonal colonization provides for a reduction and retention of phytophagous population at the economic threshold of harmfulness during the entire vegetation period. The use of fungicides based on pathogenic bacteria of the Bacillus genus and antagonist fungi of the Trichoderma genus against scab is eff ective only in the years unfavorable for the development of the disease. The results obtained form the basis for a biologized resource-saving technology for exploitation of intensive apple orchards. This technology contributes to increased soil fertility, reduced chemical and pesticide load, and increased productivity of horticultural agrocenosis under the conditions of the Crimea and southern Russia.

Microbial species pool-mediated diazotrophic community assembly in crop microbiomes during plant development.

Plant-associated diazotrophs strongly relate to plant nitrogen (N) supply and growth. However, our knowledge of diazotrophic community assembly and microbial N metabolism in plant microbiomes is largely limited. Here we examined the assembly and temporal dynamics of diazotrophic communities across multiple compartments (soils, epiphytic and endophytic niches of root and leaf, and grain) of three cereal crops (maize, wheat, and barley) and identified the potential N-cycling pathways in phylloplane microbiomes. Our results demonstrated that the microbial species pool, influenced by site-specific environmental factors (e.g., edaphic factors), had a stronger effect than host selection (i.e., plant species and developmental stage) in shaping diazotrophic communities across the soil-plant continuum. Crop diazotrophic communities were dominated by a few taxa (~0.7% of diazotrophic phylotypes) which were mainly affiliated with Methylobacterium, Azospirillum, Bradyrhizobium, and Rhizobium. Furthermore, eight dominant taxa belonging to Azospirillum and Methylobacterium were identified as keystone diazotrophic taxa for three crops and were potentially associated with microbial network stability and crop yields. Metagenomic binning recovered 58 metagenome-assembled genomes (MAGs) from the phylloplane, and the majority of them were identified as novel species (37 MAGs) and harbored genes potentially related to multiple N metabolism processes (e.g., nitrate reduction). Notably, for the first time, a high-quality MAG harboring genes involved in the complete denitrification process was recovered in the phylloplane and showed high identity to Pseudomonas mendocina. Overall, these findings significantly expand our understanding of ecological drivers of crop diazotrophs and provide new insights into the potential microbial N metabolism in the phyllosphere.IMPORTANCEPlants harbor diverse nitrogen-fixing microorganisms (i.e., diazotrophic communities) in both belowground and aboveground tissues, which play a vital role in plant nitrogen supply and growth promotion. Understanding the assembly and temporal dynamics of crop diazotrophic communities is a prerequisite for harnessing them to promote plant growth. In this study, we show that the site-specific microbial species pool largely shapes the structure of diazotrophic communities in the leaves and roots of three cereal crops. We further identify keystone diazotrophic taxa in crop microbiomes and characterize potential microbial N metabolism pathways in the phyllosphere, which provides essential information for developing microbiome-based tools in future sustainable agricultural production.

Biological activity of sod-podzolic soils at different levels of radioactive contamination

The biological (enzymatic) activity of sod-podzolic soils has been investigated in the zone of mandatory resettlement and in the alienation zone of the Chornobyl Nuclear Power Plant (CNPP) under the influence of ionizing radiation. Gas chromatographic methods were used to determine potential nitrogenfixing (nitrogenase) activity, biochemical methods were applied to study the activity of hydrolytic enzymes (cellulase and protease) responsible for the decomposition of plant residues in the soil, as well as enzymes involved in oxidative-reductive reactions of organic matter transformation (catalase and polyphenoloxidases). Statistical analysis was also employed. The results of the conducted research indicate that a relatively low increase in the total dose rate in the radioactive contamination area (from 0.2 to 1.6 µGy/h) at Polygon No. 1 (the zone of mandatory resettlement near the village of Khrystynivka, Narodychi district, Zhytomyr region) stimulated potential nitrogenase activity of soil diazotrophs and the activity of both hydrolytic enzymes and oxidoreductases. High dose rates (up to 22.2, 61.6, and especially up to 84.0 mGy/h) at Polygon No. 2, located in the alienation zone of the CNPP directly in the area of the former Red Forest, led to a decrease in soil enzymatic activity. Thus, the obtained results unequivocally demonstrate the different nature of the impact of ionizing radiation levels on the biological activity of sod-podzolic soils. The more radioactive soil in the zone of mandatory resettlement stimulates the enzymatic activity of soil microbiota. This could be attributed to adaptive changes in the development and activity of microorganisms or changes in the composition of their communities, with a prevalence of radio-tolerant microbiota representatives. It is also possible that the manifestation of a radiobiological effect, such as radiation stimulation (radiation hormesis), accelerating the growth and development of microorganisms, may occur. In the alienation zone of the CNPP, with high radioactive contamination, the negative influence of ionizing radiation on the metabolism of soil microorganisms is preserved. The obtained results are highly correlated with the indicators of the abundance of nitrogen-fixing microorganisms in the investigated soils, as well as microorganisms representing the saccharolytic (fungi and cellulolytic bacteria) and peptolytic (ammonifiers) pathways of plant residue degradation, as previously demonstrated by us.

Comparing the benthic nitrogenase activity and diazotrophic community assembly of three large river-connected freshwater lakes in eastern China

Biological nitrogen fixation (BNF) is a crucial process that provides bioavailable nitrogen and supports primary production in freshwater lake ecosystems. However, the characteristics of diazotrophic community and nitrogenase activity in freshwater lake sediments remain poorly understood. Here, we investigated the diazotrophic communities and nitrogenase activities in the sediments of three large river-connected freshwater lakes in eastern China using 15N-isotope tracing and nifH sequencing. The sediments in these lakes contained diverse nitrogenase genes that were phylogenetically grouped into Clusters I and III. The diazotrophic communities in the sediments were dominated by stochastic processes in Hongze Lake and Taihu Lake, which had heterogeneous habitats and shallower water depths, while in Poyang Lake, which had deeper water and a shorter hydraulic retention time, the assembly of the diazotrophic community in the sediments was dominated by homogeneous selection processes. Temperature and water depth were also found the key environmental factors affecting the sediment diazotrophic communities. Sediment nitrogenase activities varied in the three lakes and within distinct regions of an individual lake, ranging from 0 to 14.58 nmol/(kg·hr). Nitrogenase activity was significantly correlated with ferric iron, total phosphorus, and organic matter contents. Our results suggested that freshwater lake sediment contain high diversity of nitrogen-fixing microorganisms with potential metabolic diversity, and the community assembly patterns and nitrogenase activities varied with the lake habitat.

Production of organomineral fertilizers based on local raw materials and nitrogen-fixing microorganisms

This article deals with production of organomineral fertilizers based on local raw materials cattle dung local ores (Kyzilkum phosphorite flour and Navbahor bentonite) and nitrogen-fixing microorganisms. Based on the experiments the following results were obtained. During 60 days the raw materials selected for the experiment were used in optimal proportions: cattle dung: bentonite: nitrogen-fixing microorganisms solution (100:5:0-4) and the main chemistry of organomineral fertilizers obtained on the basis of cattle dung. bentonite. phosphorite flour and nitrogen-fixing microorganisms. Composition (CD:B:PF:NFM=100:5:5:(0-4)) was analyzed. The physico-chemical and commercial properties of the obtained new type of organomineral fertilizers were studied. The contents of organomineral fertilizer samples were analyzed by modern physicochemical methods. Composting cattle dung with local ores and processing the resulting mixture with a solution containing nitrogen-fixing microorganisms allows to further increase humic substances. assimilable forms of phosphorus and. most importantly. increase. Due to the biofixation of atmospheric molecular nitrogen. the amount of nitrogen increased by 3.4- 4.6 times.

Soil salinity effects on nitrogen fixers and cellulose decomposing microorganisms

This article presents data on the effect of soil salinity on the activity of nitrogen-fixing and cellulose-degrading microorganisms in alluvial soils of widely irrigated meadows in the Bukhara region. According to it, the activity of nitrogen-fixing and cellulose-decomposing microorganisms was studied as a control in non-saline soils, and scientific data was presented on how the activity of these bacteria changes in weakly saline, moderately saline, and strongly saline soils in the order of increasing levels of salinity, and which of the easily soluble salts in water had the greatest effect on it.

Bog bacterial community: data from north-western Russia.

Wetlands occupy up to 35% of the boreal biome in Russia, according to various estimates. Boreal bogs are global carbon sinks, accounting for more than 65% of the soil carbon stored in the wetland ecosystems of the world. The decomposition of plant residues is one of the most important components of the carbon cycle in wetland systems, while the violation of their fragile balance due to climate change increases the rate of mineralisation of organic matter and releases large amounts of carbon to the atmosphere. The biochemical processes occurring in a peat deposit determine the intensity of the destruction of organic matter and gas exchange. However, the microbial communities of the boreal ombrotrophic bogs, regulating those processes, are poorly studied. Hence, a study of the prokaryote communities of the peat deposits of the southern White Sea coastal ombrotrophic bogs (mostly spread in north-western Russia) was carried out. The taxonomic composition of archaea and bacteria sampled from the deposit's depth of 0-310 cm was studied using high-throughput sequencing of V4 sites of 16S rRNA gene by Illumina technology. As a result, 105 species belonging to 19 phylums were identified. The dominant specific phyla were Pseudomonadota, Acidobacteriota and Verrucomicrobiota, the non-specific phylum being Desulfobacterota. Various groups of methanogenic, methylotrophic and nitrogen-fixing microorganisms were identified. Shannon's biodiversity ranged from 3.5 to 4.6 and ChaO1 - from 232 to 351, decreasing within the depth.

The influence of microbial preparations on the biological activity of the rhizosphere and the productivity of winter triticale

The article presents the results on the effect of microbial preparations on the biological activity of the rhizosphere and the productivity of winter triticale. The microbiological and biochemical indicators of the biological activity of the winter triticale rhizosphere were studied against the background of the use of microbial preparations agrofil, mizorin, rhizobact of the RZHF brand and the FZhF brand. Data were revealed on the increase in the number of nitrogen-fixing microorganisms and actinomycetes when using agrofil, on the growth of micromycetes, actinomycetes, cellulose-decomposing microorganisms when treated with mizorin, the number of ammonifying microorganisms when treated with rhizobact preparations of the FZhF brand and the RZhF brand. Data on the beneficial effect of microbial preparations on the enzymatic pool of the winter triticale rhizosphere are presented. A high activity of phosphatase and peroxidase was noted when treated with the drug rhizobact brand FZhF, polyphenol oxidase and peroxidase when using the drug rhizobact brand RZHF, invertase and catalase when inoculated with the drug agrofil. Conclusions are formulated on the decrease in urease activity and the increase in indicators of productivity elements for all variants of the experiment.

Influence of firefighting fluorosynthetic film forming foam on soil microbocenosis

Per- and polyfluoroalkyl substances (PFASs) are a group of over 5000 different chemicals that are used in a wide range of industrial applications and consumer products. Perfluoroalkyl substances have unique properties, such as high chemical stability and surface activity, which leads to their widespread use in medicine, science and everyday life. Aqueous film forming foams (AFFFs) are complex proprietary formulations that contain percent levels of PFASs as well as solvents and hydrocarbon surfactants which, when combined, afford AFFF the functionality required for its purpose. Firefighting foams, such as AFFF, are used primarily to control fires involving flammable liquids such as fuel and oil. AFFF suppresses fire by producing a film over the fuel/oil fire that effectively starves the fire of oxygen. The carbon-fluorine bond makes these compounds extremely strong and stable. This chemical and thermal stability allows these substances to persist in the environment without breaking down. While biological effects of single PFAS have been studied, the effects of PFAS-containing mixtures, such as AFFF, are unknown. The environmental effects of firefighting foam pollutants are generally considered in terms of their toxicity and their biodegradability. Firefighting foams have been found to have a negative impact on the environment (e.g. can remove oxygen from aquatic environment in turn killing aquatic fauna). The effect of PFAS on the microorganisms is not sufficiently studied. To date, there are few studies on the structure and dynamics of microbes in the presence of per- and polyfluoroalkyl substances. Moreover, the results are contradictory. In this regard, it is important to study the impact of various PFAS chemicals on the microorganisms. The article presents the results of the effect study of a fluorosynthetic film forming foam, the main component of which is perfluorinated organic acid, on soil microorganisms, namely ammonifiers, oligonitrophils and nitrogen-fixing microorganisms, yeasts and molds, actinobacteria, and cellulose-degrading bacteria. It was accomplished by plating a sample of the soil that has been serially diluted in water and enumeration of colony forming units (CFU) per gram of soil. The number of soil microorganisms was counted two weeks and three months after contamination with a fluorosynthetic film forming foam. The control sample was unpolluted soil. The sample of soil (1.0 g) was mixed and suspended with a 10 ml of water in a tube for isolation and enumeration of microorganisms. The sample was shaken vigorously to separate organisms from the colloidal material surrounding soil particles. Obtained suspension was serially diluted from 10-2 to 10-6. Aliquot of each dilution was plated onto suitable agar medium. Meat-peptone agar, wort agar, starch-ammonia agar, ashby's agar and hutchinson's agar were used to isolate different groups of microorganisms from gray forest soil and to study the effect of film forming foam on them. The plates were incubated at 28 °C for 3–14 days and the results are expressed as CFU per gram of soil. Colonies of bacteria on meat-peptone agar and ashby's medium were counted after 3–4 days, yeasts and fungi on wort agar after 4–5 days and actinobacteria on starch-ammonia medium after 7–10 days. The number of colonies of cellulose-degrading microorganisms was counted after 14 days cultivation. Firefighting fluorosynthetic film forming foam led to the soil microbial community restructuring and a microbial diversity decrease. The study revealed a decrease the number of different groups of soil microorganisms two weeks after the pollution with the firefighting fluorosynthetic film forming foam, in particular ammonifiers by 2 times compared to the control, nitrogen-fixing microorganisms by 2.7 times, actinobacteria by 4.7 times, yeasts and fungi by 2.8 times. Three months after soil contamination with AFFF the number of nitrogen-fixing microorganisms, actinobacteria, yeasts and fungi increased by 1.85, 1.2 and 2.6 times compared to the control respectively. The number of ammonifiers and cellulose-degrading microorganisms decreased by 1.7 and 5.0 times compared to the control respectively.